Mobile communication systems have been generally developed to provide voice services while guaranteeing user mobility. Such mobile communication systems have gradually expanded their coverage from voice services through data services up to high-speed data services. However, as current mobile communication systems suffer resource shortages and users demand even higher-speed services, development of more advanced mobile communication systems is needed.
To meet this demand, the 3rd generation partnership project (3GPP) has been working to standardize specifications for the long term evolution (LTE) system as a next generation mobile communication system. The LTE system aims to realize high-speed packet based communication supporting a data rate of about 100 Mbps. To this end, various approaches have been considered, such as reducing the number of nodes on a communication path through simplification of the network architecture and bringing wireless protocols as close as possible to wireless channels.
Meanwhile, in the data service, unlike the voice service, resources to be allocated are determined according to the amount of data to be transmitted and the channel conditions. Hence, in a wireless communication system such as a mobile communication system, the scheduler manages allocation of transmission resources in consideration of the amount of available resources, the channel conditions, and the amount of data to be transmitted. This is also applied to the LTE system, which is one of the next generation mobile communication systems, and the scheduler located at the base station manages and allocates radio transmission resources.
With the development of broadband wireless transmission technology and terminals supporting various functions, there is a demand for a variety of services. In particular, Multimedia Broadcast Multicast Services (MBMS) is a technology that can provide a mobile broadcast service through a cellular mobile communication network. Recently, discussions have been made to provide LTE-based public safety services using evolved MBMS (eMBMS) technology (hereinafter, eMBMS and MBMS may be used interchangeably).
Unlike a point-to-point transmission service, the MBMS service is a point-to-multipoint transmission service that enables the base station to transmit the same packet to multiple terminals in one cell, thereby increasing the efficiency of utilization of radio resources. In addition, the LTE-based MBMS service employs a multi-cell transmission scheme enabling multiple base stations to simultaneously transmit the same packet. Using such a multi-cell transmission scheme, the terminal receiving the MBMS service may obtain a diversity gain at the physical layer, increasing the transmission efficiency.